WARNING: Spoilers for Legion season 3, episode 2.
Legion has revealed how David intends to defeat the Shadow King and reconcile with his former friends in Division 3 - by rewriting the past. Legion season 2 ended with David put on trial by his friends for assaulting his girlfriend, fellow mutant Syd, by erasing her memory of their relationship troubles and sleeping with her. David and Lenny escaped, and by the beginning of season 3 had started a commune. But Division 3 are still hunting David - not only because of his crimes against Syd, but because he's still destined to destroy the world.
But David knows Division 3 will never stop coming, so he's formulated a plan to set things right. In the Legion season 3 premiere, he recruited a young mutant named Switch, who has the ability to time travel. Switch is still a novice when it comes to using her powers, but David can see the raw potential her abilities hold, and plans to utilize them for his own purposes.
But how exactly is David's plan with Switch? He has a specific scheme, but also a broader new purpose, which could very well lead to the apocalyptic day Division 3 is trying to prevent.
David Wants To Change The Past To Save Himself From The Shadow King
David explains to Switch that he believes himself to be a good person who has been manipulated and abused by the Shadow King, the mutant who quite literally haunted David for the majority of his life. David seems to believe that changing that single moment in his own past will be enough to save him, if not necessarily his friends.
This is a bad idea for many, many reasons, the most obvious of which is that changing the past almost never works that cleanly; erasing a defining moment of his life could have much direr consequences than David may realize. And as he makes explicitly clear, David's first priority is self-preservation at all costs. He's still unable to acknowledge what he did to Syd was a crime, or even morally questionable; to Syd's horror, David still believes she's in love with him deep down, and that they will reunite after this minor rough patch. And while the Shadow King's effect on his overall life is not in question, David had been free of him for months by the time he assaulted Syd; he's simply unwilling to take responsibility for his actions, feeling the world owes him for the years of agony he endured, no matter his transgressions.
David is fully devoted to his delusions now, which makes him as dangerous as he's ever been. But Switch is still unsure of the limits of her powers, and David largely dismisses her warnings of demons lurking in the time hall. Could David's desire to fix his own life be the catalyst for his doomsday prophecy? If nothing else, this is the moment of no return for Legion - David Haller is unquestionably the villain of this story.
Legion Is Borrowing From Its Own Source Material - And Green Lantern?
David's attempt to rewrite history has its roots in the character's comic book origins. In the mid-90s X-Men comics, David went back in time in an attempt to assassinate Magneto, but he accidentally killed Professor X - his biological father - instead, kicking off the line-wide crossover event Age Of Apocalypse, a grim alternate reality where the fortunes of both mutants and humanity are wildly altered without Charles Xavier around.
With that in mind, it's hard to overlook the fact we'll be meeting Legion's version of Xavier this season, played by Games Of Thrones and Doctor Who alum Harry Lloyd. Given the fact that Lloyd is far too young to be the present-day version of David's father, it's likely Xavier will encounter his adult son in the relative past. It's never made explicit what - if any - role Xavier and the X-Men play in Legion's world, but fans of the iconic telepath may want to brace for some dark days.
Legion taking cues from its source material is no great surprise, even if it's largely eschewed any sort of straight adaptation in favor of series creator Noah Hawley's more eccentric tastes. The much stranger - and more interesting - parallel is to a DC Comics stalwart who underwent a radical, massively controversial change in the mid-90s himself - Green Lantern. After the destruction of his hometown, Coast City, Earth's primary ring slinger Hal Jordan found himself overcome with grief, and he attempted to use his powers to recreate the city and its murdered citizens. This was a gross ethical violation, and the Guardians of the Universe - the Green Lanterns' ancient, diminutive masters - demanded Hal give up his power ring. Instead, Hal went on an unprecedented killing spree, taking out dozens of fellow Lanterns, the Guardians, and even snapped the neck of his old enemy Sinestro. Hal sucked the power of the Green Lantern's central battery dry, making himself the cosmically powerful Parallax. He became so obsessed with rewriting history to "make things right" that he very nearly wiped out all of existence in the crossover event Zero Hour.
Beyond the obvious similarities, David and Hal serve as inversions of each other. It was eventually revealed that Hal was infected by an elemental fear parasite - also called Parallax - which drove him to violent insanity in his weakest moment. Even so, Hal paid a price for his forced misdeeds; after he was freed from Parallax, it would take years before Hal would earn back the respect and trust of all of his superhero friends and colleagues, and the jury's still out on Batman.
David has finally managed to shake the demon that has lived inside of his mind for so most of his life, but he now has to reckon with the fact that the Shadow King either warped him beyond repair, or that he was always going to end up a toxic person, justifying his transgressions through his mental illness. David's inability to recognize and reckon with that dark truth, to have the self-awareness to realize he's wrong and must answer for his crimes, is the reason Hal Jordan is a hero, and he's not.
What David's Plan Means For The Rest Of Legion Season 3
David's ultimate plan suggests a dark road ahead for Legion season 3. Even if the current plan doesn't work out like David hopes, he can presumably go back and try it as many times as he wants. As the Shadow King said himself, it's virtually impossible to defeat someone who can go back in time to warn themselves. And there's an even darker ramification here, another callback to the Green Lantern storyline - if David believes the current timeline is a mistake he's going to fix, what's stopping him from simply murdering anyone who gets in his way? It's easy to imagine David justifying such an act - he's not really killing anyone if they'll still be around after the timeline is changed, right?
Even as David's former friends have continued to hunt him with murderous intent, he's been reluctant to use lethal force against them. But with his time travel plot now in place, he likely sees his friends as unfortunate alternate reality shells of themselves that he must overcome; murdering them may not be his first choice, but he no longer seems like he'd have trouble taking that ultimate, irreversible step. If David's current scheme doesn't go exactly like he thinks it will, the body count at Division 3 may get much larger, as Legion begins its endgame.